Gas turbine engines commonly have one or more combustors surrounding the engine shaft between a forward compressor and an aft turbine. The turbine has one or more circular arrays of rotating blades alternating axially with stationary vanes. Combustion gas from the combustors is ducted to the first row of turbine blades. Critical clearance exists between the blade tips and the surrounding combustion gas path shroud. An increase in this clearance reduces engine efficiency and indicates wear. Current methods for measuring blade tip clearance require removal of at least the upper half of the turbine outer casing, and the use of feeler gauges. However, removing the casing changes stresses in the engine such that the measurement may not accurately represent the clearances in the assembled turbine.